What is a duel ? How do I duel another user ?

Hero members of Fitocracy have an option for initiating duels with their followers and the other user doesn't need to be a Hero to participate. But only a Hero can create a duel by clicking the icon of two crossed swords displayed on profile pages.

http://i.imgur.com/SWOzRyk.png

As a competition between two users, the person creating the event will be asked to designate how long the duel will last. It can be for one day or several months!
There are several options for dueling. These include:

Free for all - The winner is determined by who can accumulate the most points in the designated time period.

Heaviest widowmaker - A competition to see which participant can perform the heaviest widowmaker . A widowmaker is a barbell squat of 20 reps.

Most swimming distance - The objective is to log the most distance swimming.

Most cycling distance - By logging outdoor cycling or mountain biking, both users compete for most distance cycled outside.

Most distance on foot - Whoever runs, walks, or hikes the most distance is the winner of this challenge. The activities that accrue to this duel are outdoor running, trail running, treadmill running, outdoor walking, treadmill walking, light walking, interval/sprint running, and hiking .

Triathlon challenge - Users compete for most points from logging outdoor running, trail running, outdoor cycling, mountain biking, and swimming .

Heaviest barbell deadlift - A competition to see who can log the heaviest traditional deadlift. Sumo, romanian, and other variations are not included.

Heaviest barbell bench press -This duel centers on who can log a heavier barbell bench press.

Most push ups- Regular push-up, Divebomber, Clap, Diamond, Close Grip, Wide Arm all count to total amount of push ups logged between the two users.

Monkeying around - Highest number of chin-ups and pull-ups (includes assisted and weighted varieties) logged determines this duel winner

Drop and give me plenty - See who can get the most points from push-ups, pull-ups, crunches, running, and sit-ups. (Included activities: crunch, push-up, pull-up including assisted and weighted, sit-up, outdoor running, and trail running)

Fire fighter challenge - A competition to see who can log the most flights of stairs climbed. This is logged as ' Walked up the stairs (in lieu of the elevator) '.

Most distance cycled (including stationary) - Again, most cycling distance but with more options such as Cycling, Mountain Biking, Cycling (stationary), and Spinning.

Most running distance - To win, both users log for most distance from running, trail running, interval/sprint running, and treadmill running.

Heaviest barbell squat - The competitors will both log barbell squats to determine who can squat the heavier amount of weight.

There are also four duels where the winner is decided based on Wilks Coefficient score. "The Wilks Coefficient or Wilks Formula is a coefficient that can be used to measure the strength of a powerlifter against other powerlifters despite the different weights of the lifters. " (Source: Wikipedia) By factoring Wilks Coefficient, female and male users can fairly battle one another. These duels are:

Heaviest squat - Barbell squat only of at most 10 reps.

Heaviest bench press - Barbell bench press only of at most 10 reps.

Heaviest deadlift - Barbell deadlift and sumo deadlift of at most 10 reps .

Heaviest big three - Barbell bench press, barbell squat, barbell deadlift including sumo deadlift for at most 10 reps.